A light emitting diode (LED) is a semiconductor device that emits light when an electric current flows. More specifically, an LED refers to a PN junction diode made of an optical semiconductor such as gallium arsenide (GaAs) or gallium nitride (GaN). It is an electronic component that converts electrical energy to light energy.
In recent years, blue LEDs and ultraviolet LEDs based on nitrides that have good physical and chemical properties have emerged, and LEDs have found many applications because white light or other monochromatic light can be generated by using blue or ultraviolet LEDs and fluorescent materials.
LEDs have many advantages over other light sources, including longer lifetime, smaller size, lighter body, directional light emission, low voltage operation, strong resistance to impact and vibration, and being free of preheating time and complicated driving. For these reasons, LEDs can be used in various applications. For example, LEDs are increasingly used in more diverse applications such as compact lighting devices of mobile terminals, general indoor or outdoor lighting devices, automotive headlamps, and backlight lighting devices for large LCD displays.
Also, in recent years, LED lamps have been increasingly used in place of incandescent lamps and other bulb-type lighting devices.
In lighting, the term “hemispherical intensity distribution” refers to a characteristic in which light is not emitted only in a specific direction but is emitted in all directions. Generally, incandescent lamps have a good luminous intensity distribution, but the light intensity distribution of LED lighting is usually dependent on the structure of an LED driver and the structure of an LED substrate.
Regarding FIGS. 1 through 3, FIGS. 1 and 2 are perspective views illustrating an external form and a detailed structure of a typical LED bulb, and FIG. 3 is a diagram illustrating the luminous intensity distribution of a typical LED bulb.
As illustrated in the drawing, a conventional LED bulb has a structure in which a plurality of LEDs are disposed on one surface of an LED substrate in a widthwise direction perpendicular to a longitudinal direction of the LED substrate. Thus, the direction of light emission is limited, resulting in a poor luminous intensity distribution at the rear side.
In addition, a conventional LED bulb uses a heat sink to solve the problem of heat generation, the heat sink resulting in an increase in volume and weight and an increase in manufacturing cost of the LED bulb, and finally resulting in an increase in the product price.